Soft tissue
Fibroblastic / myofibroblastic tumors
Solitary fibrous tumor (extrapleural)

Author: Ashley Gullett, M.D. (see Authors page)
Editor: Jerad M. Gardner, M.D.

Revised: 12 September 2016, last major update June 2013

Copyright: (c) 2003-2015,, Inc.

PubMed Search: Solitary fibrous tumor [title] soft tissue

Cite this page: Solitary fibrous tumor (extrapleural). website. Accessed October 21st, 2016.
Definition / General
Clinical Features
  • Usually middle-aged adults (median age 50 years)
  • Wide anatomic distribution; essentially arises from any soft tissue or visceral location
  • Rarely causes paraneoplastic hypoglycemia due to insulin-like growth factor production
  • Slow growing painless mass, usually benign; histologically malignant tumors may be grossly infiltrative and 15 - 20% may metastasize; rarely histologically benign tumors metastasize
Prognostic Factors
  • Poor prognostic factors: size > 10 cm, > 4 mitoses / 10 HPF, cellular atypia, positive margins, malignant histology (Cancer 2002;94:1057), although histology may have less significance in retroperitoneum (Urol Oncol 2008;26:254)
Case Reports
Clinical Images

Images hosted on PathOut servers:

Skin, courtesy of Mark R. Wick, M.D.

Gross Description
  • Well circumscribed, nonencapsulated or partially encapsulated, solitary, lobulated masses that measure 5 - 8 cm on average with multinodular, white, firm cut surface
  • Necrosis and infiltrative margins are associated with locally aggressive or malignant tumors
Gross Images

Images hosted on other servers:

Tan-white tumor with focal necrosis

Tumor of omentum

Micro Description
  • Patternless architecture of hypo- and hypercellular areas separated by thick, hyalinized collagen with cracking artifact and staghorn vessels
  • Perivascular sclerosis
  • Bland and uniform oval to spindle cells dispersed along thin parallel collagen bands, cells have minimal cytoplasm, small elongated nuclei and indistinct nucleoli
  • Some have myxoid change (Virchows Arch 2009;454:189), mast cells, adipose tissue or multinucleated giant cells
  • Minimal pleomorphism
  • No atypia, no / rare mitotic figures
  • Malignant SFT: hypercellular, moderate to marked atypia and nuclear pleomorphism, hyperchromasia, tumor necrosis, 4+ mitotic figures / 10 HPF including atypical mitoses, infiltrative borders
Micro Images

Images hosted on PathOut servers:

Moderately cellular fibroblastic appearance

Parallel arrays of collagen are separated by fibroblastic nuclei

Scant cytoplasm and uniform
spindled nuclei, note the thin bands
of intercellular collagen

Case of the week #29 (dermis images)

Courtesy of Mark R. Wick, M.D.:

Storiform growth

Staghorn blood vessels

Skin lesions

Various images

Images hosted on other servers:

Patternless appearance and collagenous stroma

"Patternless" growth pattern

Partly "neural-like" tumor cells


Epithelioid nodules near fusocellular areas

Biphasic pattern

Round, polygonal cells

CD34 and bcl2

Positive Stains
Negative Stains
Electron Microscopy Description
  • Myofibroblasts, fibroblasts
Molecular / Cytogenetics Description
  • Cytogenetic abnormalities in most tumors 10 cm or larger; no consistent genetic event
Differential Diagnosis